In the Figures, the same element presented in different figures will have the same reference numeral. The first digit of a reference numeral will indicate the first figure in which that reference numeral is utilized.
This invention relates in general to buried isolation layers and relates more particularly to such layers in GaAs devices. In a variety of applications, it has been found advantageous to produce insulating or semiinsulating regions to produce lateral confinement of certain currents. For example, in the quantum well semiconductor injection laser structure of FIG. 1 (see E. Kapon et al, "Patterned quantum well semiconductor injection laser grown by molecular beam epitaxy", Appl. Phys. Lett. 52(8), Feb. 22, 1988), after the laser structure 11 has been produced, lateral current confinement is obtained by bombarding regions 12 and 13 with protons. These high energy protons produce a semiinsulating region by damaging the lattice in the implanted region. Unfortunately, this method produces a current confinement region 14 more than 2 microns, which is wider than desired and therefore does not provide as strong confinement as can be achieved with this invention.
In the graded index separate-confinement heterostructure (GRINSCH) AlGaAs/GaAs laser of FIGS. 2A and 2B (see Fujin Xiong, et al "High efficiency single quantum well graded-index separate-confinement heterostructure lasers fabricated with MeV oxygen ion implantation", Appl. Phys. Lett. 54(8), Feb. 20, 1989), after fabrication of the laser structure, a gold mask 21 is used during a step (shown in FIG. 2A) of implanting O.sup.+ ions to produce a pair of oxygen doped regions 22 and 23. When an n-type substrate is used, after annealing this structure, a pair of semiinsulating regions 24 and 25 are produced to provide lateral confinement of current through active region 26 of the laser. Unfortunately, this conductive region bounded by insulating regions 24 and 25 is also wider than desired.